The present invention relates generally to pedometers and more particularly to calibrated pedometers that can be recalibrated for enhanced accuracy. The device correlates a calibrated stride length and stride rate to an actual stride length for use in calculating the distance traveled. Actual stride rates, lengths, or distances traveled are then compared to the calibrated values stored in a table and the calibrated values are adjusted accordingly to recalibrate the pedometer. Further, initial calibration stride rates and lengths can be generated from empirical gender and height data. Finally, recalibration can be performed using an algorithm when the differences between actual values and calibrated or calculated values exceeds a predetermined amount.
Pedometers are known which include devices or algorithms for determining the distance a person travels on foot. For example, U.S. Pat. No. 4,371,945 discloses an electronic pedometer that calculates distance by electronically measuring the length of each stride taken by a user. Stride length is measured by ultrasonic waves generated by an ultrasonic module strapped to one leg and an ultrasonic detector worn on the other leg. A program compensates for a variety of measurement errors and the results are displayed on a wrist-mounted display after being transmitted by VHF waves from the leg to the wrist.
U.S. Pat. No. 4,771,394 discloses a computer shoe with a heel-mounted electronic device with an inertia footstrike counter, a timer, a sound generating device, a battery, and a gate array for counting time and footstrikes to calculate distance and running time as a function of stride time. Although recognizing the important relationship of stride length and foot speed, the shoe in this patent requires data from at least 15 test runs or walks and the data must be user-entered in pairs of footstrikes and elapsed time to cover a pre-determined distance. Further, user adjustments of time must be performed to accommodate start and stop times, and the number of counted footstrikes is increased one percent to overcome inherent errors in the inertia step counter. The shoe-mounted device is subject to damage from impact, dirt, and water, and requires a stay-at-home computer with which to interface. There is no means disclosed to transmit data to a wrist-mounted display device or an xe2x80x9con-boardxe2x80x9d computing device that provides xe2x80x9creal timexe2x80x9d data to a runner.
U.S. Pat. No. 4,855,942 discloses a pedometer and calorie measuring device that includes a wrist-mounted step counter and a fixed stride length to calculate distance traveled. Wrist-mounted step counters are known to be inaccurate because they assume a step for every arm movement. Even with error correction, such a device will provide less accurate step counts than a leg or waist-mounted counter. Further, fixed stride lengths do not take into account the fact that stride length varies with rate of movement.
U.S. Pat. No. 5,117,444 discloses a pedometer and calibration method with two calibration modes. First, a user travels a predetermined xe2x80x9chalf-distancexe2x80x9d for the device to count and store the number of strides in that distance. Next, the user travels a second distance with the step counter comparing actual steps to the steps in memory and a current trip memory are incremented by a tenth of a xe2x80x9cwhole unitxe2x80x9d distance. There is no correlation between stride length and stride rate which requires the user to re-calibrate the device when walking as opposed to running.
U.S. Pat. No. 5,475,725 discloses a pulse meter with pedometer function to determine pace and pulse rate of a user. The meter uses pulse wave base data compared to actual pulse wave data rates.
U.S. Pat. No. 5,476,427 discloses a pace display device utilizing a base rate for traveling pre-set distances in successive trials. The device calculates step counts and rates, and compares actual step count rates to display data to a user for comparison of present running rates to previous rates.
Many pedometers require calibration by individual users so that the stride length for that user is the basis for any subsequent distance calculation. These pedometers can be recalibrated only by repeating the initial calibration ritual.
For example, some pedometers require a user to measure his or her stride length over a 10 foot section, which involves a fairly complicated procedure of measuring out this distance, counting steps (and partial steps), and doing the math to convert this distance to inches. However, if the pedometer is used for both walking and running, the user will have to recalibrate the pedometer to account for different stride lengths used in these two activities. This same procedure is necessary if the user ever wishes to recalibrate the pedometer.
Thus, there is a need for a pedometer that can be easily calibrated and recalibrated to enhance its accuracy. There is also a need for an accurate pedometer that monitors pace to measure the intensity of a workout.
Thus, there is a need for a simple, but highly accurate, pedometer that displays distance traveled, pace, speed, heart rate, and other important information on an easily read wrist-mounted or waist-mounted device.
The present invention overcomes problems and shortcomings in the prior art by providing a pedometer including a data processor programmed to: create an initial calibration table of initial stride rates and lengths to be compared to an actual stride rate for deriving a corresponding actual stride length, use a recalibration stride rate over a known distance traveled, determine a calculated distance traveled using the initial calibration table and the recalibration stride rate, compare the calculated distance traveled with the known distance traveled to determine the difference, if any, between the two, and replace an initial stride length with a revised stride length that is a function of the initial stride length and the recalibration stride length. The pedometer can further include: a strap connected to the pedometer for releasably securing the pedometer to a user; and a heart rate monitor connected to the strap.
The pedometer""s data processor can be further programmed to: calculate each stride length as an average of all the stride lengths calculated during each calibration run; calculate each stride rate as a function of the average stride rate calculated during each calibration run; to calculate an initial stride rate as a function of the average stride rate from a plurality of calibration runs, and to recalibrate a stride rate as a function of the difference between the initial stride rate and the subsequent stride rate; and/or recalibrate the stride rate based on an algorithm.
The invention is also directed to pedometer data processor programmed to: create an initial calibration table of initial stride rates and lengths for comparison with an actual stride rate for deriving a corresponding actual stride length and distance traveled, calculate a recalibration stride rate length corresponding to a known stride rate over a known distance traveled, determine a calculated distance traveled using the initial calibration table and the known stride rate, compare the calculated distance traveled with the known distance traveled to determine a difference between the two, and adjust the initial calibration table to a revised stride length that is a function of the average between the initial stride length and the known stride length. The data processor can be further programmed to: replace an initial stride length with a recalibrated stride length only when the difference between the calculated distance traveled and the actual distance traveled varies by more than a predetermined amount; recalibrate the pedometer only when the difference between the calculated distance traveled and the actual distance traveled is greater that two percent; create the initial calibration table from predetermined empirical data that can be gender-specific; and/or create the initial calibration table by calculating and storing stride rates and lengths derived from average stride rates and lengths in a series of calibration runs performed by a user.
Also, the present invention is directed to a cadence pacing device including: a step counter; a clock; and a data processor in communication with the step counter and the clock, and the data processor is programmed to calculate a pace by dividing a number of steps counted by the step counter by a period of time measured by the clock, and further programmed to compare the pace to predetermined range of paces and generating a warning signal when the pace is outside of the predetermined range of paces, wherein the warning signal can be communicated to a user. The cadence pacing device can be arranged so that the step counter, clock, and data processor are mounted on a strap and the cadence pacing device further comprises: a heart rate monitor mounted on the strap.
The device can include a waist, chest, or leg-mounted stride counting device, a transmitter, and a wrist-mounted receiver/display device that provides highly accurate travel distances and other information. The device includes a data processor that stores base stride length and rate data from traveling a pre-determined distance and compares that to actual stride rate data to calculate actual distance traveled, speed, and pace. The invention recognizes the interdependency of stride length and stride rate and uses that relationship to provide superior distance-calculating accuracy.
The invention also provides for improved display of relevant data on a wrist-mounted display that receives digital signals from devices worn on other body parts such as legs, waist, and chest. Transmitters that can send coded signals are desirable because they will not interfere with similar devices worn by other users in the vicinity.
The accuracy of the device can be enhanced using two different inventions. Both methods use an algorithm that adjusts a stride length based on actual stride rates. The two methods are known as the Shifting Curve method and the Unique Curve method. The Shifting Curve method uses a single algorithm that is modified to match an individual""s running or walking characteristics. This algorithm is defined as: Actual Stride Length=Base Stride Length+Base Stride Length*(((Actual Stride Ratexe2x88x92Base Stride Rate) N)/Base Stride Rate); where N is either an average value or a derived value from a plurality of samples.
This method also includes a variation for calculating an actual stride length including steps of: timing a first user run of a predetermined distance; counting the total number of strides in the user first run; dividing the first run distance by the stride count to obtain a base stride length; dividing the stride count by the first run time to obtain a base stride rate; counting strides during a user""s second run to obtain an actual stride rate; calculating the actual stride length using the formula: Actual Stride Length=Base Stride Length+Base Stride Length *(((Actual Stride Ratexe2x88x92Base Stride Rate )N)/Base Stride Rate); wherein N is an average value or a derived value.
The average value variation can be refined by comparing Base Stride Rate to Actual Stride Rate to determine a percentage difference; and using N=1 when the Actual Stride Ratexe2x89xa6Base Stride Rate*1.02 and using N=3 when Actual Stride Rate greater than Base Stride Rate*1.02. One embodiment uses a plurality of sample runs over known distances to derive an accurate N value for each individual.
The preferred method is referred to as the Unique Curve method that creates a unique or custom curve for each individual reflecting the unique relationship between stride rate and stride length at two or more sample points, and the rate of change between, above, and below these points to obtain an accurate stride length for incremental changes in stride rate.
The present invention can be used for walking only by: taking two walks of a known distance, but at significantly different pacesxe2x80x94one relatively slow and one relatively fast. The steps counted by the pedometer over the known distance can be used to calculate a steps per second rate for both walks. These rates can then be used to generate a graph or table by interpolating and extrapolating the two rates to arrive at a stride length for any reasonable rate being walked by the user. This stride length can then be used to calculate a highly accurate distance being walked by a user of the pedometer of the present invention.
When used for running only, or running and walking, calculating stride length is similar to the above walking method, except more walks and runs are conducted over fixed distances at a variety of rates. A computer-stored card can be used during subsequent trips to find a very accurate stride length for a given step rate. The chart is unique for each user, and in this manner, a highly accurate step length can be calculated from a given step rate to calculate distance traveled, accurate speeds, optimum heart rates, optimum workout times at given heart rates, etc.
Other features and benefits of the present invention will be apparent from the following detailed description of the invention.